21212009218 has 4 divisors (see below), whose sum is σ = 31818013830. Its totient is φ = 10606004608.

The previous prime is 21212009213. The next prime is 21212009227. The reversal of 21212009218 is 81290021212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 13562232849 + 7649776369 = 116457^2 + 87463^2 .

It is not an unprimeable number, because it can be changed into a prime (21212009213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5303002303 + ... + 5303002306.

Almost surely, 2^21212009218 is an apocalyptic number.

21212009218 is a deficient number, since it is larger than the sum of its proper divisors (10606004612).

21212009218 is a wasteful number, since it uses less digits than its factorization.

21212009218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10606004611.

The product of its (nonzero) digits is 1152, while the sum is 28.

The spelling of 21212009218 in words is "twenty-one billion, two hundred twelve million, nine thousand, two hundred eighteen".